1. Field of the Invention
The invention relates to a frequency converter for an electric motor having a power portion, an intermediate circuit component and a control and regulation component.
2. Description of the Prior Art
Frequency converters are, for example, applied for the drive of electric motors of pump units, fans and other machines. Freqequency converter applications typically were exclusively considered for motors of more than 1 KW. However, an increasing miniaturization of the frequency converter and the manufacture on a large scale now allows the application of frequency converters to motors in the region between 50 W and 1000 W to be economically practical. In particular with pump units the application of frequency converters is particularly advantageous since with this, pump units may be provided which in spite of a relatively small diameter realize a large delivery flow due to high rotational speed.
A submersible unit for such a pump unit is for example known from DE 197 27 202 A1. With such an arrangement all components of the frequency converter are to be accommodated within a cylindrical housing of a comparatively small diameter. In contrast however to other applications with which the axial and radial constructional length of the motor where possible is not to be increased, one seeks to arrange the components of the frequency converter in a flat manner on the outer periphery of the motor housing. Again with other applications the frequency converter where possible is to be accommodated in the terminal box of the motor, thus on the rectangular-parallelpiped-shaped housing. Furthermore the construction is to be modified for the respective application such that the waste heat arising in the power part may be reliably led away.
Since the manufacturing costs of such a frequency converter depend very heavily on the number of pieces to be manufactured, it is desirable for different applications to be able to apply the same components. It is known to divide up the frequency converter into components and to arrange these individual components for example in a circuit board manner. Functionally a frequency converter consists of an input circuit, of an intermedate circuit and of a power circuitxe2x80x94also called inverse rectifierxe2x80x94as well as of a control and regulation circuit. It is known to integrate the power circuit of the frequency converter into a semiconductor component or into a semiconductor element, to construct the input as well as the intermediate circuit on a common circuitboard as well as the control and regulation circuit on a further circuitboard. With this construction, particularly large construction components such as for example capacitors and coils of the intermediate circuit may be arranged separate from the circuitboard.
This object is achieved according to the invention by a frequency coverter for an electric motor including a power part integrated in a common semiconductor component, an intermediate circuit component, and a control and regulation component. Each of the intermediate circuit component and the control and regulating component comprise a circuit board. Electric connections between the semiconductor component and the control and regulating component comprise a circuit board. Electric connections between the semiconductor component and circuit boards of the intermediate component and the control and regulation component are made via a plurality of sheet metal sections positioned and mechanically connected via a cast body of the power part, such that the sheet metal sections comprise leads of the power part.
The basic concept of the present invention is to integrate the lead connections and connections within the frequency converter where possible into one component, specifically into that of the power partxe2x80x94this comprises essentially the power circuit and where appropriate further power electronics such as for example the input circuit. For this the power part is particulary useful to be selected since the power part requires lead connections to the input circuit or to the mains supply, to the intermediate circuit, to the control and regulation circuit and to the motor. These electrical connections may all be integrated into one component, wherein the leads are formed of sheet metal sections, thus from punched sections which on the one hand are inexpensive to manufacture and on the other hand offer a high intrinsic stability and a sufficiently large conducting cross section. These leads lead directly to the circuitboards of the connection components, where they are contacted, be it by way of soldering or welding or also by way of a plug-and-socket connection. These components fixed together with the semiconductor component by way of a cast mass are inexpensive to manufacture, and specifically with a differing arrangement of the connections without having to change anything on the basic design construction. Simultaneously these additional design elements may be used for fastening the semiconductor component. The semiconductor component as a rule specifically requires an intensive cooling, which usually is effected by a heat conducting bearing of this onto a heat distributor. Via the cast body which either encompasses the semiconductor component on at least three sides or also encloses it, be it partly or completely, there may be effected a fastening, be it via clamping clips or screw closures, rivets or likewise, without mechanically overloading the semiconductor component.
The semiconductor component containing the power part is usually rectangular-parallelpiped-shaped and flat, wherein the lead connections are led out at the narrow end-faces. With such a construction it is particularly advantageous when the leads facing the intermediate circuit component are led out to one side of the cast body or of the semiconductor component, the leads facing the control and regulation component to the opposite distant side of the cast body and the leads facing the motor to a side displaced by 90xc2x0 to this. Disregarding the fact that this arrangement permits a crossing-free leading of the leads, thus a leading of the leads in one plane, this arrangement has the advantage that the intermediate circuit component as well as the control and regulation component, according to application, may be arranged at a different angle to the power component. There may therefore for example be selected an arrangement with which these three components are adapted to the curvature on the outer periphery of a motor. By way of a bending-up about in each case 90xc2x0 with respect to the power component there may also be achieved an arrangement which becomes essentially rectangular parallelpiped-shaped or is insertable into a cylindrical body. With a straight arrangement in contrast it will result in a two-dimensionally constructed frequency converter. Since the electrical connections leaving the power part are formed by sheet metal sections which usefully lie such that their flat sides lie parallel in the plane of the semiconductor component or parallel thereto, these may be bent up practically in any manner along the sides of the power part component. As long as they in this region are encompassed by the cast body only the cast mould it to be correspondingly adapted or the bending up to be carried out before the cast body is completely solidified.